354 FXUS06 KWBC 241902 PMDMRD Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks NWS Climate Prediction Center College Park, MD 300 PM EDT Sun August 24 2025 6-10 DAY OUTLOOK FOR AUG 30 - SEP 03, 2025 During the 6-10 day forecast period, a broadly amplified mid-level ridge with associated positive 500-hPa height anomalies remains forecast across Canada, with an area of troughing further upstream over the Bering Sea, aligning with a trend toward a positive phase of the Pacific-North American Pattern (+PNA) going into September. Compared to yesterday, there is a greater westward extension of positive height anomalies across the Gulf of Alaska, particularly in the GEFS. Also of note is that todays 6z GEFS is weaker and more offshore with troughing depicted over the Eastern Pacific compared to the 0z run, and also yesterdays GEFS solutions, which depicted this troughing closer to or along the West Coast of the CONUS. Models remain in good agreement regarding troughing over the eastern U.S. Todays manual 500-hPa height blend for the 6-10 day period depicts positive height anomalies over most of Canada extending into parts of the northwestern and north-central CONUS, and over much of Mainland Alaska, Southeast Alaska, and the Alaska Peninsula. Negative height anomalies are depicted from the Central Plains eastward to the Atlantic Coast. Negative height anomalies are also favored over the Aleutians, increasing in magnitude farther west. A weak mid-level flow pattern is predicted in the vicinity of Hawaii, with near- to slightly above-normal heights favored. A cooler air mass is forecast to be entrenched across the eastern half of the CONUS at the start of the period, with a stationary frontal boundary settling across the Gulf of America and the Florida Peninsula. The Weather Prediction Center is predicting negative daytime maximum temperature anomalies of at least -10 deg F across some parts of the Central Plains at the outset of the period. While these anomalies are favored to moderate later in the period, the period as a whole is still likely to tilt below-normal, justifying increased below-normal temperature probabilities (greater than 60 percent) over the region. Further East, temperature anomalies of -5 to -10 deg F will likely bring an early taste of Fall in time of the Labor Day Holiday weekend. Conversely across the West, enhanced chances for above-normal temperatures are favored, with the 6z GEFS coming more in line with the warmer ECENS and CMCE solutions. There remains some uncertainty over the Four Corners where the ECENS (GEFS) is cooler (warmer), resulting in slightly enhanced probabilities of near-normal temperatures. Above-normal temperature chances are increased over portions of south Texas and the Florida Peninsula to the south of the stationary frontal boundary. Near-to above-normal temperature chances are increased over southern and eastern Mainland and Southeast Alaska consistent with the GEFS and ECENS reforecast tools and above-normal mid-level heights. Weakly enhanced probabilities of below-normal temperatures are forecast over parts of the Aleutians and the northwestern Mainland. Above-normal temperatures are favored for nearly all of Hawaii, excluding southern parts of the Big Island where near-normal temperatures are favored, supported by the consolidated forecast tool. The aforementioned stationary front favors elevated above-normal precipitation chances across the Gulf and Southeast Coasts, the Florida Peninsula, and extending back into the Four Corners and Southern Plains. To the north of this boundary, underneath surface high pressure, near- to below-normal precipitation chances are increased, with the highest chances for below-normal precipitation over the Great Lakes and Ohio Valley, supported mostly by the uncalibrated and reforecast ECENS, as well as the analogs. Troughing near the West Coast favors an increase in onshore flow, although the signals are reduced compared to yesterday given a more offshore and weaker trough being depicted in the guidance, particularly the 6z GEFS. While much of the West continues to lean toward above-normal precipitation aided in part by low climatologies, the probabilities are reduced compared to yesterday. Troughing over the Bering Sea favors increased chances of above-normal precipitation over much of Mainland Alaska and the Aleutians, with increased below-normal precipitation odds over Southeast Alaska due to more influence from the ridging over Canada. Near- to above-normal precipitation is favored across Hawaii. The official 6-10 day 500-hPa height blend consists of 30% of Today's 6z GFS Ensemble Mean centered on Day 8, 40% of Today's 0z European Ensemble Mean centered on Day 8, and 30% of Today's 0z Canadian Ensemble Mean centered on Day 8 FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Average, 3 out of 5, due to good model agreement regarding the mid-level height pattern early in the period, offset by increasing uncertainty, particularly in regards to temperatures over the western U.S. 8-14 DAY OUTLOOK FOR SEP 01 - 07 2025 Mid-level ridging and positive 500-hPa height anomalies are forecast to persist across Canada during week-2. While the GEFS and CMCE solutions depict the positive height anomaly center remaining across central Canada, the ECENS indicates the largest positive height anomalies becoming centered more to the west across Southeast Alaska, and weaker height anomalies and some hints of troughing developing over central and eastern Canada later in the period. The mid-level flow pattern across the CONUS is forecast to decrease in amplitude due to troughing initially forecast over the East weakening. A weak trough may persist off the West Coast of the CONUS underneath the positive height anomalies building to the north, and troughing also remains predicted over the Bering Sea, although this feature is weaker in magnitude compared to the 6-10 day period. Todays manual 500-hPa height blend for week-2 depicts two +90 meter positive height anomaly centers across central Canada and Southeast Alaska, with +30 meter positive anomalies extending into portions of the Northwest and Northern Plains. Positive height anomalies are forecast throughout most of Alaska excluding the central and western Aleutians where closer to normal heights are favored. Near- to below-normal heights are forecast over much of the eastern half of the CONUS, with closer to normal heights over most of the West. Near-to above-normal heights are forecast to persist across Hawaii. Given the decreasing amplification in the mid-level height pattern over the CONUS, the resultant temperature forecast is more uncertain. Enhanced probabilities for below-normal temperatures are forecast from the Central Plains to the Eastern Seaboard, but probabilities are reduced compared to the 6-10 day period and are mainly tied to higher confidence earlier in the period. Warmer air may also begin to migrate eastward, favoring increasing chances for near- to above-normal temperatures over much of the Northern Tier. Above-normal temperature probabilities remain elevated along most of the Gulf Coast and over the Florida Peninsula to the south of a stationary frontal boundary. As discussed in the 6-10 day outlook, models are leaning more toward a warmer solution across the West and this is reflected in the forecast. There is more uncertainty over portions of the Southwest due to increasing East Pacific tropical moisture, and over the Rockies due to model differences similar to that of the 6-10 day period, resulting in near-normal being favored over these areas. High probabilities of above-normal temperatures are highlighted over much of Mainland and Southeast Alaska, with elevated chances of near- to below-normal temperatures favored across the Aleutians. Above-normal temperatures remain favored over Hawaii. A stationary front continues to support increased chances of above-normal precipitation across the coastal Southeast and Gulf Coast, and extending back through the High Plains and Four Corners. To the north of this boundary, the ECENS is drier compared to the GEFS across the East, with some uncertainty into how quickly moisture advects into the region as the troughing weakens. Near-normal precipitation is generally favored for much of the Interior East, with a slight tilt toward increased odds for below-normal precipitation over parts of the Great Lakes and Northeast. Despite the low amplitude pattern, enhanced onshore flow across the West Coast favors elevated above-normal precipitation probabilities over much of the West, given low climatologies this time of year. Continued tropical cyclone activity across the Eastern Pacific may also contribute to enhanced moisture over the Southwest toward the end of the period. Odds for near-to above-normal precipitation continue to be elevated over much of Mainland Alaska and the Aleutians associated with troughing over the Bering Sea early in the period. Larger positive height anomalies downstream support increased chances for below-normal precipitation over Southeast Alaska. Near- to above-normal precipitation is favored across Hawaii. The official 8-14 day 500-hPa height blend consists of: 30% of Today's 6z GFS Ensemble Mean centered on Day 11, 40% of Today's 0z European Ensemble Mean centered on Day 11, and 30% of Today's 0z Canadian Ensemble Mean centered on Day 11 FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5, due to decreasing amplification of the 500-hPa pattern and weakening signals in the temperature and precipitation guidance by the end of the period. FORECASTER: Thomas Collow Notes: The notation for the categorical forecast indicated on the maps is the same as that in the tables: A-above N-near normal B-below The temperature map shows regions with > 33% chance of being warmer (orange, "A"), colder (blue, "B"), or close to (unshaded, "N"). Historical average values for the calendar period of the forecast (dashes, "f"). Labels on the shaded lines give the probability (> 33%) of the more likely category (B or A). Probability of N is always < 40%. The precipitation map shows regions with > 33% chance of being wetter (green, "A"), drier (tan, "B"), or close to (unshaded, "n"). Historical median values for the calendar period of the forecast (dashes, "inches"). Labels on the shaded lines give the probability (> 33%) of the more likely category (B or A). Probability of N is always < 40%. In the southwest and other climatologically dry regions - there will be a greater than 33.3% chance of no precipitation and occasionally even a normal (i.e. Median) value of zero - especially during the dry seasons. In such cases a forecast of near normal is effectively a forecast of little or no precipitation. The climate prediction center uses 1991-2020 base period means as reference in the climate outlooks. The next set of long-lead monthly and seasonal outlooks will be released on September 18. Analogs to the 5 day mean observed pattern centered 3 days ago (D-3) for the region from 20N to 70N latitude and 175E to 60W longitude include the 5 day periods centered on the following dates: 19940816 - 19560808 - 19540830 - 19930804 - 19940828 Analogs to the 7 day mean observed pattern centered 4 days ago (D-4) for the region from 20N to 70N latitude and 175E to 60W longitude include the 7 day periods centered on the following dates: 19930803 - 19940816 - 19940828 - 19560807 - 20040809 6-10 DAY OUTLOOK TABLE Outlook for Aug 30 - Sep 03, 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A A NRN CALIF A A SRN CALIF A N IDAHO A A NEVADA A A W MONTANA A A E MONTANA A A WYOMING N A UTAH N A ARIZONA N A COLORADO N A NEW MEXICO N A N DAKOTA A A S DAKOTA N A NEBRASKA B A KANSAS B A OKLAHOMA B A N TEXAS B A S TEXAS A A W TEXAS B A MINNESOTA N A IOWA B N MISSOURI B N ARKANSAS B A LOUISIANA B A WISCONSIN B B ILLINOIS B N MISSISSIPPI B A MICHIGAN B B INDIANA B B OHIO B B KENTUCKY B B TENNESSEE B N ALABAMA B N NEW YORK B B VERMONT B B NEW HAMP B B MAINE B B MASS B N CONN B N RHODE IS B N PENN B B NEW JERSEY B N W VIRGINIA B B MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B N S CAROLINA B A GEORGIA B A FL PNHDL B A FL PENIN A A AK N SLOPE N A AK ALEUTIAN N A AK WESTERN N A AK INT BSN A A AK S INT A A AK SO COAST A A AK PNHDL A B 8-14 DAY OUTLOOK TABLE Outlook for Sep 01 - 07 2025 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A A NRN CALIF A A SRN CALIF N N IDAHO A A NEVADA A A W MONTANA A A E MONTANA A A WYOMING N A UTAH N A ARIZONA A A COLORADO B A NEW MEXICO N A N DAKOTA A A S DAKOTA N A NEBRASKA B A KANSAS B A OKLAHOMA B A N TEXAS N A S TEXAS A A W TEXAS N A MINNESOTA N N IOWA B A MISSOURI B A ARKANSAS B N LOUISIANA A A WISCONSIN N N ILLINOIS B N MISSISSIPPI N A MICHIGAN A N INDIANA N N OHIO N N KENTUCKY B N TENNESSEE B N ALABAMA B N NEW YORK N B VERMONT N N NEW HAMP N N MAINE N B MASS N N CONN N N RHODE IS N N PENN N N NEW JERSEY B N W VIRGINIA N N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B N S CAROLINA B N GEORGIA B N FL PNHDL N A FL PENIN A A AK N SLOPE A A AK ALEUTIAN B A AK WESTERN A A AK INT BSN A A AK S INT A A AK SO COAST A A AK PNHDL A B LEGEND TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN B - BELOW B - BELOW THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE. FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS PMDMRD. $$